Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an electrophotographic apparatus.
Description of the Related Art
An electrophotographic photosensitive member including a support, an undercoat layer formed on the support, and a photosensitive layer formed on the undercoat layer and containing an organic charge generating substance and an organic charge transporting substance has been used as electrophotographic photosensitive members for electrophotographic apparatuses. The undercoat layer has a charge-blocking function and thus suppresses the charge injection from the support to the photosensitive layer. Consequently, formation of image defects such as black spots is suppressed.
In recent years, charge generating substances having higher sensitivity have been used. However, such an increase in the sensitivity of charge generating substances results in an increase in the amount of charge generated. As a result, charge easily remains in the photosensitive layer, which poses a problem in that ghosts are easily formed. Specifically, a so-called “positive ghost” phenomenon in which an image density increases only in a portion irradiated with light in the previous rotation or a so-called “negative ghost” phenomenon in which an image density decreases only in a portion irradiated with light in the previous rotation easily occurs in an output image.
Japanese Patent Laid-Open No. 2006-221094 discloses a technique in which an undercoat layer includes a metal oxide and a compound having an anthraquinone structure in order to suppress such a ghost phenomenon.
In recent years, with an increasing number of electrophotographic apparatuses having a color function, higher speed and higher image quality have been required for such electrophotographic apparatuses, and higher performance has been also required for electrophotographic photosensitive members. For example, the degradation of image quality caused by a ghost phenomenon needs to be suppressed in various environments.
However, the technique disclosed in Japanese Patent Laid-Open No. 2006-221094 still has room for improvement because the degradation of image quality caused by a ghost phenomenon is not sufficiently suppressed.